Summary:
The observed geological and geochemical characteristics of the La Pava and Quema-Quemita gold deposits at Cerro Quema are consistent with those of volcanic hosted, epithermal, high sulfidation (HS) gold-silver deposits.
The Cerro Quema project is spatially associated with the E-trending regional Rio Joaquin fault system. The fault zone is 30 km long and shows evidence of reverse dip-slip movement. It juxtaposedAzuero Igneous basement rocks against Azuero Arc Group rocks. Mesoscale open folds in the region have SW plunging axes and moderate limb dips, indicative of dextral transpression with dominant reverse dip-slip motion (Isaac Corral 2016). The Cerro Quema mineralized zone lies 1.5 to 3km north of the Rio Joaquin fault. Longo has postulated sinestral movement along the most prominent of the NE striking faults, possibly resulting in dismemberment of an originally continuous mineralized zone with the La Pava zone being the left lateral offset of the Quema-Quemita deposit (Longo 2018).
Distinct styles of mineralization observed today are due primarily to supergene effects on the primary mineralization. The known mineralized zones (Pava, Quema-Quemita, Idaida-Caballito, Pelona) were likely similar to Caballito before oxidation. Three mineralization styles are observed:
1. Epithermal high sulfidation Au mineralization, associated with variably intensely developed advanced argillic alteration of dacitic rocks with local areas of silicification and leaching resulting in vuggy silica alteration typical of high sulfidation epithermal deposits. Gold is associated with pyrite and enargite deposition (Longo 2018) and is present as submicroscopic grains and as invisible inclusions in pyrite (Isaac Corral 2016).
2. Cu-Au mineralization, exemplified by the Idaida-Caballito mineralized zone, that differs from the other mineralized zones in its relatively high Cu content and a strong Cu-Au association. Copper mineralization is associated with hypogene pyrite, bornite, chalcopyrite, and enargite and occurs as an irregular breccia body with sulfide cement. Type 2 mineralization postdates formation of the Type1 high sulfidation mineralization and is superimposed upon it, but formed as part of the same mineralizing event as ore fluid chemistry evolved from high sulfidation to intermediate sulfidation conditions iscrete gold mineralized zones have been identified by drilling and surface mapping along an EW trending zone of hydrothermal alteration of dacitic volcanic rocks of the Rio Quema Formation. The mineralized belt extends from La Pava West at the western end to La Pelona, 11 km further east.
3. Cu-Au mineralization at La Prieta, an altered and mineralized zone centred upon a Miocene quartz diorite intrusion, occurs 2.6 km south of the main E-W belt of mineralization. Disseminated and fracture-controlled pyrite and chalcopyrite is associated with intermediate argillic alteration conditions (Longo 2018). This mineralized zone has not been studied in detail nor drilled.
Mineralization style 1 corresponds to the mineralized deposits at La Pava and Quema-Quemitaand style 2 corresponds to the Caballito Cu-Au deposit. Mineralized zones thus far identified, and their type, high sulfidation (HS) or intermediate sulfidation (IS) and metals of interest (gold, copper, silver), include:
- La Pava West, HS, Au;
- La Pava, HS, Au;
- Chontal, HS, Au;
- Quema-Quemita, HS, Au;
- Sombrero, HS, Au;
- Idaida, IS, Cu, Au;
- Caballito, IS, Cu, Au;
- Howler, LS vein, Au;
- Picadores, unstudied, Au;
- Placetas, unstudied, Au;
- La Pelona, HS, Au;
- La Prieta (south of main trend, younger), Cu, Au.
Vuggy quartz alteration, occurring as irregular funnel and tabular shaped bodies, is made up of microcrystalline anhedral quartz grains, disseminated pyrite, barite, rutile, covellite, bornite, and chalcocite (Longo 2020) and traces of sphalerite (Isaac Corral 2016). At depth, vuggy quartz contains disseminated pyrite, enargite, chalcopyrite, and tennantite (Isaac Corral 2016). The vuggy texture results from acid leaching of once present hornblende and plagioclase. Oxidation of sulfides resulted in formation of gossanous and intensely iron oxide pigmented exposures at surface. Vuggy quartz alteration zones are contained within an irregular halo of advanced argillic alterationdefined by silicification accompanied by the presence of alunite and/or dickite, pyrophyllite, barite, illite, and diaspore. The advanced argillic alteration assemblage observed at Cerro Quema is typical of high sulfidation epithermal deposits.
Epithermal high sulfidation gold mineralization is hosted predominantly by silicified and leached zones found within broader zones of advanced argillic alteration. Advanced argillic and argillic alteration zones host lesser amounts of gold mineralization.
Complete oxidation is observed in the uppermost portions of both the La Pava and QuemaQuemita mineralized zones.
At Quema-Quemita, complete oxidation forms an irregular zone mimicking topography and extends to depths of as much as 100m below the present topographic surface. Nearly the entirety of the vuggy silica altered zone is oxidized, and in places the oxide boundary forms a downward prominence following the shape of the vuggy silica zone, apparently as a function of increased downwardpercolation of meteoric waters within the highly permeable vuggy silica zones. The contact with underlying non-oxidized rock is generally sharp. At Quema-Quemita, the oxidation boundary often corresponds with the limit of vuggy silica or argillic alteration.
At La Pava the oxidation zone mimics topography but is more irregular than that of QuemaQuemita, and pods of oxidized material within unoxidized material, and vice versa, are more common. At La Pava oxidation extends to maximum depths of 150m below surface but is typically less than 100m. In contrast to Quema-Quemita, at La Pava, significant volumes of the vuggy silica alteration zone are not oxidized and the oxidation boundary does not closely follow the alteration zones.
At Caballito, the mineralized zone lies almost entirely beneath the oxide zone and Caballito comprises sulfide mineralization.
The mineralization at Cerro Quema is hosted by a submarine dacite dome complex developed during the period ~65 to 75 Ma during a subduction related magmatic event (Longo 2020). Hydrothermal mineralizing fluids associated with a younger magmatic event estimated at ~55 to 49 Ma (Isaac Corral 2016) mineralogically altered the dacitic rocks, creating advanced argillic mineral assemblages an leached silicified rock (vuggy silica). Multiple hydrothermal plumes related to the magmatic event were localized at structural intersections and affected the rocks, resulting in Au and Cu-A deposition, dominantly in vuggy silica rock and hydrothermal breccias, forming irregular tabular mineralized zones. Meteoric oxidation and supergene leaching resulted in Cu depletion and Au enrichment in the oxidized vuggy silica bodies. An oxidation zone defined by complete destruction of sulfide minerals, extends to depths of as much as 150m below surface, resulting in oxidized gold deposits at La Pava and Quema-Quemita, and at La Pava, supergene Cu concentrations developed below the oxide gold zone. At both La Pava and Quema-Quemita, unoxidized primary sulfide mineralization with variable amounts of Au and Cu are present, but do not form any of the Mineral Resources or Reserves.
The La Pava gold deposit is hosted in dacitic dome rocks of the Rio Quema Formation, comprising dacitic porphyritic intrusive rocks and extrusive rocks that include dacitic lavas, hyaloclastic carapace breccias, dacitic tuffs and dacitic volcaniclastic sedimentary strata.
The Quema-Quemita gold deposit is analogous to the La Pava deposit, and may be a structurally offset portion of the same (Longo, Cerro Quema update June 29, 2018, private report prepared for Orla Mining Ltd 2018).